California Gov. Jerry Brown signed a controversial bill into law on Tuesday that prohibits families from using “personal belief” or religious exemptions to keep their children from getting vaccinations in order to attend public school.

Senate Bill 277“eliminates the exemption from existing specified immunization requirements based upon personal beliefs,” and only allows exemption from future immunization requirements “deemed appropriate by the State Department of Public Health for either medical reasons or personal beliefs.”

The bill was created in response to a measles outbreak at Disneyland in December where one individual spread the virus to 131 people, sending 20 the hospital. The Orange County Register reported that out of the 81 patients whose vaccination status was known, “70 percent had not been vaccinated.”

“The science is clear that vaccines dramatically protect children against a number of infectious and dangerous diseases,” Brown wrote in a letter to the state Senate. “While it’s true that no medical intervention is without risk, the evidence shows that immunization powerfully benefits and protects the community.”

A group in opposition to the bill, California Coalition for Vaccine Choice, claims that it “impacts children in private or public elementary or secondary school, child care center, day nursery, nursery school, family day care home, or development center” by eliminating “a parent’s right to exempt their children from one, some, or all vaccines, a risk-laden medical procedure.”

According to the bill’s co-sponsors, Democratic Senators Richard Pan and Ben Allen, if a parent chooses to not vaccinate their child, then he/she will not be allowed to attend public or private school, and will have to either be home-schooled, attend a multifamily private home-school, or use public school independent study.

Although all 50 states require immunization for school children, 20 states allow exemptions for personal beliefs, and California follows Mississippi and West Virginia in becoming the only states to ban religious exemptions.

Reuters reported that Brown’s support for the new vaccination law “marks an about-face for the former seminarian who three years ago opposed eliminating the religious exemption for school vaccines.”